1. Field of the Invention
The present invention relates to a chemical composition and its use for remediation of waste streams including those from municipal and industrial sources containing high levels of contaminants such as fat, oil, grease, soluble and insoluble heavy metals, organic matter and inorganic matter. The composition includes natural minerals such as clay, zeolites, apatite, Dolomitic lime, fly ash, cement, coagulants, and flocculants which are either cationic, anionic or nonionic in nature.
2. Description of Prior Developments
Waste streams generally contain contaminants such as fat, oil, grease, heavy metals, organic substances such as phenolics, chlorinated compounds, and inorganics such as fluoride, sulfate, phosphate, cyanide, chromates, arsenic and selenium, at levels considered hazardous to the environment and which could pose a risk to public health. Such contaminants must be removed or their levels reduced to meet government discharge standards prior to discharging the waste into the environment.
Waste streams are generally treated by chemical, physical or mechanical means, or by combinations thereof. Techniques used in conventional wastewater treatment for removing emulsified soluble or floating oils, suspended solids, heavy metals, organic and inorganic matters basically involve several steps such as demulsification, oil skimming, metal precipitation, flocculation, and settling. Each step takes place in a separate tank and the entire treatment requires multiple adjustments of pH and the addition of acid, emulsion breakers (demulsifiers), lime/caustic, coagulants, and polymer solutions.
This conventional multi-step process is time consuming and has a high demand for equipment, i.e., it requires a number of treatment tanks equipped with agitators, pumps, liquid chemical dispensers and feed lines, chemicals, manpower, and energy. In each step, wastewater may be recirculated several times for retreatment to effect the maximum removal of contaminants, before it goes to the next step.
Moreover, the generated solid waste typically contains high levels of heavy metals and other hazardous substances which are usually leachable. The waste therefore requires further treatment to render the solid waste non-hazardous before it can be safely disposed. The cost of the disposal of hazardous waste is three to four times the disposal cost of nonhazardous waste.
The use of chemical agents for treating wastewater is disclosed in U.S. Pat. Nos. 3,956,117, 3,428,558, 3,968,036, 4,167,481, 4,517,094, 5,336,704, and 5,415,808. These earlier inventions, however, suffer from disadvantages relating to their limited applications, i.e., the chemical agents are not stand-alone products. For example, U.S. Pat. No. 3,956,117 discloses the use of cationic polymers for removal of oil; U.S. Pat. Nos. 3,428,558, and 5,415,808 disclose polymeric flocculants and their use in the removal of suspended particles; U.S. Pat. Nos. 4,167,481 and 5,336,704 disclose chemical compositions for removal of metals; and U.S. Pat. Nos. 3,968,036 and 4,517,094 disclose methods for removal of organics.
None of these earlier inventions discloses a single agent or composition that is capable of simultaneous removal of contaminants such as oil and grease, suspended solids, heavy metals, and other organic and inorganic matter. Moreover, in most cases, prior treatment processes are also tedious and laborious such as those disclosed in U.S. Pat. Nos. 4,167,481 and 4,517,094 or those inventions wherein a conventional multi-step process is required when polymeric flocculants are used. Most importantly, these earlier inventions are not cost effective and generate solid wastes that are normally hazardous and must be further treated prior to disposal.
More recently, attention has been focused on the development of a single product system for treatment of waste streams, such as disclosed in U.S. Pat. Nos. 3,953,330, 4,332,693, 4,415,467, and 4,765,908. These products suffer from disadvantages due to non-versatility, i.e., they are generally applicable to a specific type of waste stream, e.g., oil, metals, or organic contaminated waste streams. Moreover, their manufacturing processes are complex, the compositions work in a narrow range of pH, they are slow to react with contaminants, and they produce solid waste that may not pass the Toxicity Characteristic Leaching Procedure test (TCLP) instituted by the US EPA. These products also do not work well in the presence of chelating and complexing agents, they usually require a pretreatment step to break the chelate or a post treatment step with a polishing agent, and they are costly to use on a commercial scale.
Accordingly, what is needed is an economical single treatment agent or chemical composition for remediation of waste steams, and more particularly industrial waste streams, which is capable of simultaneously and efficiently removing up to several thousand ppm of fat, oil, grease, suspended solids, soluble and insoluble heavy metals, and other organic and inorganic matters, resulting in treated water that meets discharge standards set by environmental authorities.
A further need exists for such a single treatment agent which leads to the formation of a fast settling floc that is easily dewatered.
A further need exists for a process that removes hazardous contaminants from a waste stream and isolates them in a stabilized non-leaching matrix.
A further need exists for such an agent and process which generates solid waste that does not require further treatment in order to pass the TCLP test and does not pose a hazard to the environment once disposed in a landfill.
A further need exists for such a composition that is very versatile and works effectively over a wide pH range of, e.g. 2-12, and has an uptake capacity that is independent of the presence of surfactants, detergents, hardness, and chelating/complexing agents.
A further need exists for such a composition which produces a non-slimy sludge which does not block or clog sludge filters such as filter presses.
The present invention has been developed to meet, and does in fact meet, the needs noted above and therefore has as an object the provision of a single-composition, simultaneous-process for the treatment of wastewater that can be carried out in either a batch process or in a continuous process. In a batch process, a single treatment tank is sufficient and the treatment agent can be added manually or through a dry powder feeder. Addition of a settling tank may enhance the efficiency of the sedimentation process when treating large volumes of water.
Synergistic effects, brought about by the various components of the treatment composition, enhance the reaction rate between the composition and contaminants in the waste stream. Such effects are fully utilized in the continuous process such that the treatment can handle the incoming waste streams at flow rates as high as 1000 gal/min. The treatment composition can be fed continuously at a predetermined feed rate using automated feed equipment.
The sludge can be dewatered via a filtration system such as a vacuum filtration system, a centrifuge, and most preferably a filter press which is simple and relatively easy to maintain. Treated water is drained off and released or recycled for reuse and the solid waste is hauled away without the need for further treatment.
A further object of this invention is to provide a treatment technology that produces high quality treated water suitable for reuse in manufacturing processes without the high cost of utilizing membrane separation technology or other technologies.
A treatment agent for the remediation of waste streams has been developed in accordance with this invention for simultaneously removing virtually all contaminants in the waste stream. Contaminants removed by the treatment agent include fats, oil, grease, other organic matters, suspended solids, and soluble heavy metals which exist as positive ions such as aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, silver, tin, titanium, zinc as well as radioactive elements such as uranium, thorium, and plutonium.
In addition, the treatment agent and process according to the invention are effective in removing negative ions such as sulfate, fluoride, phosphate, hexavalent chromium, arsenic and selenium. Furthermore, the compositions of this invention are effective in lowering the levels of chemical oxygen demand (COD) and biological oxygen demand (BOD) in waste streams.
The chemical composition of the present invention can include natural aluminosilicates such as natural clays, and a blend of natural and synthetic minerals which includes natural clay, Dolomitic lime, cement, fly ash and phosphate rocks. The chemical composition of the present invention can further include, individually, zeolites, Dolomitic lime, apatite, cement, and fly ash. Additional components can include coagulating agents which are either organic, inorganic or combinations thereof, and flocculating agents which are either cationic, anionic, nonionic or combinations thereof. These ingredients work synergistically to enhance the reaction kinetics between the contaminants in the waste stream and the treatment agent, leading to an increased uptake capacity, up to several thousands of ppm, and formation of a highly stabilized waste which typically requires no further treatment in order to pass the TCLP test. The nature of contaminants present in the various waste steams and their concentrations may vary widely from case to case and therefore the percentage of each component in the composition is determined and adjusted accordingly within the scope of this invention.
Treatment agents of the present invention are very cost effective and react quickly to remove contaminants from wastewater. Such use produces a high-quality treated effluent that meets discharge standards or requirements for reuse, and also produces a stabilized solid waste. With the treatment compositions of the present invention, the treatment process, which previously has generally been a multi-step process, is now reduced to a single step and requires fewer treatment vessels and only one dispenser to deliver the treatment composition.
The treatment composition of this invention is also effective over a wide waste stream pH range, i.e., 2-12, and therefore in most applications initial and post treatment pH adjustments are not required. Additionally, the reaction between the composition of the present invention and contaminants in the waste stream is independent of the presence of chelating and/or complexing agents and, accordingly, use of polishing agents such as sulfides, dithiocarbamates and other noxious chemicals or the application of a pretreatment to break the chelate is no longer necessary.
Due to the fast reaction rate of the present treatment process and the high capacity of the treatment agents in taking up and immobilizing contaminants, a continuous treatment process can handle waste streams having flow rates as high as 1000 gal/min. Furthermore, the process of the present invention is simple and relatively inexpensive which makes it possible and affordable for small operators to set up their own treatment systems. This, in turn, reduces the demand put on treatment facilities such as publicly owned treatment works (POTW), and waste and waste treatment plants.
In summary, the present invention provides:
1. An efficient process for remediation of waste streams, particularly wastewater and groundwater;
2. Stand-alone compositions for the simultaneous uptake of oil and grease, metals, organics, phosphorus, fluoride, and suspended solids present in waste streams, and particularly industrial waste streams;
3. A process and compositions that work over a wide pH range, i.e., 2 to 12;
4. A fast treatment process that can handle flow rates up to 1000 gallons per minute in a continuous setup;
5. Formation of a dense floc that is fast settling and easy to dewater, resulting in a compact small volume of solid waste;
6. A process that generates solid waste that passes the TCLP test;
7. Treated water that meets government discharge standards;
8. Treated water of high quality that can be reused in manufacturing processes; and
9. A wastewater remediation process which is very economical.
The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention.
The present invention is directed to treatment compositions and to a treatment process for the remediation of waste streams and, more particularly, industrial waste streams, without the need for the addition of other chemicals. The treatment agents according to this invention are preferably provided in a solid homogeneous powdered form which is easily dispensed via manual measurement or automatically metered into a treatment tank in either a batch or continuous treatment process. With efficient mixing, i.e., vigorous mixing, the treatment agent is easily dispersed such that it interacts instantly with contaminants in the waste stream.
One form of the treatment composition includes, by weight percent, 5 to 85% of natural clays, a blend of natural and synthetic minerals, (such as clay, zealot, fly ash, cement, fumed silica cement and pulverized phosphate rocks), or combinations thereof; 5 to 85% of cement such as Portland cement, 2 to 23% of fly ash; 2 to 40% of a pulverized natural phosphate rock such as appetite selected from a group of hydroxyapatite, fluorapatite, and/or chlorapatite or combinations thereof; 5 to 58% of Dolomitic lime; 0 to 40% of either organic coagulants selected from a group of low molecular weight cationic polyelectrolytes such as polyamine, polydiallyldimethylammonium chloride, and polyepichlorohydrin, etc., or inorganic coagulants selected from a group of aluminum or iron containing compounds, or combinations of the organic and inorganic coagulants; and 0.2 to 5.5% of flocculating agents such as anionic, nonionic, cationic polymers, or combinations thereof. The amounts stated in the composition are based on the total weight of the composition.
The mineral blend includes from 30 to 75% w/w of natural clay, from 5 to 45% w/w of Dolomitic lime, from 5 to 30% w/w of cement and from 0.8 to 7.5% w/w of fly ash. This blend can be substituted for or combined with the natural clays and zeolites noted above as long as the overall limits on each constituent are maintained as specified. The natural clay in the mineral blend is selected from bentonite, zeolites and natural phosphate rocks, and the cement is preferably a blend of oxides of Si, Al, Fe, Mg, Ca, Mn, Na, and silicon, aluminum, iron, manganese, alkaline earth and alkali metals.
Coagulants suitable for this invention are inorganic, organic, or combinations thereof. Inorganic coagulants include iron and aluminum containing compounds such as sodium aluminates, aluminum chlorhydrate, polyaluminum chloride, aluminum sulfate, ferric chloride, ferrous sulfate, and ferric sulfate. Organic coagulants include polymeric materials such as polyamine, polydiallyldimethylamonium chloride, and polyamine epichlohydrin.
Preferred polymeric flocculating agents include high molecular weight anionic, nonionic, cationic polyelectrolytes, or combinations thereof. The nonionic polyelectrolytes are selected from a group consisting of hydrolyzed polyacrylonitrile, polyacrylamide, and acrylamide/acrylonitrile copolymer. The preferred anionic polyelectrolytes are polyacrylamide/acrylate, maleates, methacrylates, sulfonates, and 2-acrylamido-2-methylpropane sulfonate copolymers. The preferred cationic polyelectrolytes are acrylamide copolymers of dimethyldiallyammonium chloride, dialkyl aminoethyl acrylate or methacrylate quartenized with dimethylsulfate or methyl chloride, and methacrylamidopropyltrimethylammonium chloride or a combination thereof, and preferably polyelectrolytes of high molecular weight and most preferably polyelectrolytes of a molecular weight above 5 million.
A preferred treatment agent includes:
a. From 15 to 60% of natural clays, zeolites, a natural mineral blend, or combinations thereof;
b. From 15 to 65% of cement.
c. From 3 to 15% of fly ash, silica fume or a mixture thereof.
d. From 8 to 28% of hydroxyapatite, fluorapatite, chlorapatite, or combinations thereof.
e. From 7 to 45% Dolomitic lime.
f. From 0 to 28% inorganic, organic coagulants or combinations thereof.
g. From 0.5 to 2.5% flocculating agents selected from a group which consists of anionic, nonionic, cationic agents, or combinations thereof.
It should be noted that fly ash and fumed silica (silica fume) are directly interchangeable and can be substituted for one another in equal amounts. Moreover, natural clay and pulverized phosphate rocks are also interchangeable and can be substituted for one another on a one for one basis.
The following examples will further illustrate the preparation and performance of the preferred compositions in accordance with the present invention. However, it is to be understood that these examples are given by way of illustration and not limitation. In these examples, parts means parts by weight, unless otherwise noted.